Process and product

ABSTRACT

Compounds typified by N,N&#39;-polyoxyalkylene bis (pyrrolidinone-3-carboxylic acid) are useful as epoxy curing accelerators. Salts thereof, including alkali metal salts, are curing agents for isocyanurate foams.

RELATED APPLICATION

This is a division of application Ser. No. 847,642 filed Nov. 1, 1977,which is a continuation-in-part of application Ser. No. 689,409 filedMay 24, 1976, now abandoned.

FIELD OF THE INVENTION

This invention relates to novel products particularly characterized bytheir use as curing agents for epoxy resins or isocyanurate foams or asaccelerators for curable epoxy resins.

BACKGROUND OF THE INVENTION

As is well known to those skilled in the art, epoxy resins may be curedby the use of aromatic amines such as (i) methylene dianiline, (ii) thepolymeric condensation product of aniline and formaldehyde, etc. Typicalprior art curing, at elevated temperatures of 80° C. or higher, yieldsproducts which are resistant to attack by chemicals, solvents, etc.Curing of epoxy resins at ambient temperature however yields productcoatings which are undercured, brittle, without strength, and readilyattacked by many chemicals and solvents.

It is an object of this invention to provide novel products which may beused in curing systems. Other objects will be apparent to those skilledin the art.

STATEMENT OF THE INVENTION

In accordance with certain of its aspects, this invention is directed tonovel products ##STR1## wherein x is an integer 0-2, a is an integer ofat least 2; M is hydrogen, alkali metal, or quaternary ammonium when xis 0, 1 or 2; R"' is a polyoxyalkylene chain having terminal carbonatoms to which the nitrogen atoms are bonded; and the molecular weightof R"' is 200-2100, except that the molecular weight of R"' is 300-2100when x is 0 and M is hydrogen.

In accordance with certain of its other aspects, this invention isdirected to a method of curing an uncured epoxy resin in the presence ofaromatic curing agent and 1-15 parts of an accelerator ##STR2## whereinx is an integer of 0-2; a is an integer of at least 2; R"' is apolyoxyalkylene chain having terminal carbon atoms to which the nitrogenatoms are bonded; and the molecular weight of R"' is 200-2100.

In accordance with certain of its other aspects this invention isdirected to a method of preparing cured isocyanurate foam whichcomprises reacting an isocyanate with a polyol having at least twoactive Zerewitinoff-active hydrogen atoms in the presence of a blowingagent thereby forming a polyisocyanurate foam; and conducting saidreaction in the presence of 0.5-10 parts (per 100 parts of totalformulation) of a curing agent ##STR3## wherein x is an integer 0-2; ais an integer at least 2; M is alkali metal or quaternary ammonium; R"'is a polyoxyalkylene chain, of a molecular weight of about 200-2100,having terminal carbon atoms to which the nitrogen atoms are bonded.

DESCRIPTION OF THE INVENTION

The charge unsaturated carboxylic acids which may be used in practice ofthe process of this invention are characterized by the formula: ##STR4##wherein x is an integer 0-2. Valence bonds in this structure, or inothers in this specification, may be filled with hydrogen or with inertsubstituents which do not interfere with the reaction.

When x is 2, the acid may be represented by the formula (typified byalpha-methylene adipic acid): ##STR5##

When x is 1, the acid may be represented by the formula (typified byalpha-methylene glutaric acid): ##STR6##

When x is 0, the acid may be represented by the formula (typified byitaconic acid): ##STR7##

In the preferred acid, x is zero. The preferred acid is thus itaconicacid.

The polyoxyalkylene polyamines which may be used in practice of theprocess of this invention are characterized by the formula

    (R"') (NH.sub.2).sub.a

wherein a is an integer preferably 2-3 and R"' is a polyoxyalkylenechain of molecular weight 200-2100 having a terminal carbon atoms towhich the nitrogen atoms are bonded.

As will be apparent herein, in certain instances R"' will preferablyhave a molecular weight of 300-2100, and in certain instances morepreferably 400-2100.

When a is 3, an illustrative compound of molecular weight of about 400may be ##STR8## wherein f plus g plus h is 5.3 typically as availableunder the trademark Jeffamine T-403 of Jefferson Chemical Company.

The preferred amines which may be used in practice of the process ofthis invention are polyoxyalkylene diamines characterized by theformula:

    H.sub.2 N (R") NH.sub.2

wherein R" is a polyoxyalkylene chain of molecular weight of about200-2100 having terminal carbon atoms to which the nitrogen atoms arebonded.

As will be apparent herein, in certain instances R"' will preferablyhave a molecular weight of 300-2100, and in certain instances morepreferably 400-2100. R" is derived from an oxyalkylene group, typifiedby oxyethylene --CH₂ CH₂ O--, oxypropylene --OCH₂ CH(CH₃)-- etc. R" mayalso be a polyoxyethylene bearing an added polyoxypropylene (as in thecompositions marketed by Jefferson Chemical Co. under the trademarkJeffamine ED-series) typified by ##STR9##

Typical of the polyoxyalkylene diamines which may be used in practice ofthe process of this invention may be those listed in the table:

TABLE

a. the diterminal diamine of polyoxypropylene of molecular weight 427;

b. The diterminal diamine of polyoxypropylene of molecular weight 235;

c. The diterminal diamine of polyoxypropylene of molecular weight 2000;

d. The diterminal diamine of polyoxyethylene of molecular weight 600;etc.

It will be apparent to those skilled in the art that many of thesuitable polyoxyalkylene polyamines may be available as and used ascommercial mixtures of several components. Useful commercial materialsinclude those available under the trademarks Jeffamine D-, T-, and ED-etc. as marketed by Jefferson Chemical Company.

In practice of the process of this invention, according to certain ofits aspects, an equivalent amount of unsaturated carboxylic acid isadded to a reaction mixture together with one mole of polyoxyalkylenepolyamine. The reaction may be carried out in the absence of addedsolvent-diluent, but the latter may be present if desired--includingwater, toluene, etc. Water is preferably added in amount of 50 w%-200w%, say about 100% of the amine.

During the reaction, the reaction mixture is maintaned at ring-formingconditions including temperature of 80° C.-200° C., say 100° C. for 4-12hours, say 8 hours. During this period, the following reaction occurs:##STR10##

In the case of the preferred diamines, the reaction may be: ##STR11##

In the case of one preferred embodiment, itaconic acid--polyoxyethylenedi-primary amine, the reaction may be: ##STR12##

In the case of another preferred embodiment, a specific reaction may beas follows: ##STR13##

As reaction continues, the water produced by the reaction (in amount ofone mole per mole of acid reacted) may be distilled off. If desired, thewater may be removed during refluxing by azeotropic distillation with egtoluene. Typically at the end of the reaction period, the reactionmixture may be recovered and filtered, preferably in the presence ofadded filter aid such as Supercell brand.

The product so obtained is preferably worked up by stripping, as in arotary evaporator at 80° C.-200° C., say 95° C. Stripping may typicallybe carried out under vacuum of 0.1-50 mm. Hg, say 0.5 mm. Hg.

Yield is about stoichiometric.

Typical product is recovered as composition which (depending on thecomponents from which it is prepared and its molecular weight) maygenerally be characterized as a clear viscus liquid, a light brownviscous liquid, a tacky resin, etc.

These products are generally characterized by their solubility inalcohols (eg benzyl alcohol, ethanol, hexanols, etc). They areparticularly characterized by solubility in polymer systems in whichthey may find use.

These products may be used as recovered or in the form of solutions ineg benzyl alcohol. They are particularly characterized by their abilityto serve as accelerators for curing epoxy resins.

It is a feature of the process of this invention that the acids preparedby the process of this invention may serve as curing agents for epoxyresins. Salts of the noted acids, particularly the alkali-metal salts orquaternary ammonium salts (either being monobasic, dibasic, orpolybasic) serve as curing agents for isocyanurate foam systems.Illustrative salts include the monosodium salts, the di-potassium salts,the di-(tetramethylammonium) salts, the di-(tetraethylammonium) saltsetc. The salts may be prepared either by reacting the charge acid in theform of its salt (eg di-potassium itaconate) or more preferably byreacting the acid product acid with a base eg tetramethylammoniumhydroxide or potassium hydroxide.

The dialkali metal salt is preferably prepared by adding to therecovered reaction mixture an equivalent amount of eg potassiumhydroxide in 5%-30%, say 20% aqueous solution at 20° C.-80° C., say 50°C. After 10-20 minutes, say 15 minutes agitation, the reaction mixturemay be filtered through a bed of filter aid and the resulting solutionmay be used as recovered, eg as a 10%-80%, say 50% solution. If desiredthe salt may be recovered as by evaporation. Both the mono-alkali andthe di-alkali metal salts may be recovered.

In practice of certain of its aspects, this invention includes themethod of preparing a cured epoxy resin characterized by the fact thatwhen cured at ambient temperature of 20° C.-50° C., say 30° C., it isfound to possess outstanding properties particularly with respect tostrength and retention of strength after immersion in solvents. Curingagents falling outside the scope of this invention (such as eg thereaction product of itaconic acid and eg p-phenylene diamine--asdisclosed in Paytash et al. J. A. C. S. 72, 1415-6 (1950)--are notsatisfactory as curing accelerators for epoxy resins because they aregenerally high-melting solid compositions which do not readily blend inwith the viscous epoxy formulation. The novel products of this inventionare particularly characterized by their high compatibility with thecomponents of the epoxy resins. The fact that they are generally liquidsprovides a substantial advantage to the processor.

An epoxy resin which may be cured by the process of this invention maytypically be one prepared for example by the reaction of bisphenol-Awith epichlorohydrin ##STR14## in the presence of a base--preferablysodium hydroxide. After the condensation is complete, the crude resin isfreed of residual epichlorhydrin, washed well to remove salt and solubleby-products, and recovered.

Curing of 100 parts of such a resin is effected in the presence of 20-40parts, say 30 parts of an aromatic polyamine curing agent and 1-15 partsof the accelerator of this invention in eg 10-30 parts, say 20 parts ofa solution containing 10-50% of the accelerator of this invention.

Typical aromatic polyamine curing agent which may be employed is acondensation product of formaldehyde and aniline (as marketed under thetrademark JEFFAMINE AP-22). Illustrative curing agents may include:

TABLE

methylene dianiline

diamino-diphenyl ether

meta-phenylene diamine

tolylene diamine

The accelerator of this invention, preferably in the form of the freeacid, is mixed with the liquid epoxy resin and curing agent; and themixture is degassed, poured into aluminum molds, and cured typically forseven days at ambient temperature.

The product epoxy resin is particularly characterized by increasedstrength and by increased resistance to the deteriorative action of awide range of liquids.

In practice of certain of its other aspects, this invention includes themethod of preparing cured isocyanurate foams particularly characterizedby their desirably longer cream time which desirably allows morelatitude during preparation--i.e. the formulation is more mobile andhandleable during a longer period of time.

An isocyanurate foam which may be cured by the process of this inventionmay be one prepared by reacting an isocyanate typified by a phosgenatedcondensation product of aniline and formaldehyde having an NCOequivalent weight of 134 and a functionality of 2.7.

The isocyanate is preferably reacted with a polyol which has two or moreactive hydrogen atoms as determined by the Zerewitinoff method e.g. thepolyoxyalkylene polyols which may be employed in practice of thisinvention will be organic compounds having two or more reactive hydrogenatoms which will react with organic polyfunctional isocyanates to giveurethane polymers. These polyoxyalkylene polyols typically having ahydroxyl number of 100-800 preferably 200-300, say 200, may includepolyesters, polyethers, polyisocyanate modified polyesters,polyisocyanate modified polyester amides, alkylene glycols, polyamines,polyisocyanate modified alkylene glycols, etc. It will be understoodthat these polyols may have active primary or secondary hydroxyl groups.The polyol may be a hydroxyl-containing polyether or polyester includingfatty acid glycerides. Polyesters, which are a preferred type of polyol,may be obtained by esterification condensation reaction of e.g. analiphatic dibasic carboxylic acid with a glycol or a triol or mixturethereof in proportion such that the resultant polyesters may containpredominantly terminal hydroxyl groups. Dibasic carboxylic acidssuitable for preparing polyesters may include aliphatic and aromaticacids such as adipic acid, fumaric acid, sebacic acid, phthalic acid;suitable alcohols include ethylene glycol, diethylene glycol,trimethylol propane, etc. The fatty acid glycerides may include thosehaving a hydroxyl number of at least about 50 such as castor oils,hydrogenated caster oil, or blown natural oils.

Polyethers, another preferred type of polyol, may include polyalkyleneglycols, e.g. polyethylene glycols and polypropylene glycols preferablyhaving a molecular weight of at least 60. For convenience, the term"polyol" or "polyoxyalkylene polyol" may be employed to designate thesubstances having two or more active hydrogen atoms as determined by theZerewitinoff method, which may be employed in practice of thisinvention.

In one aspect of the process of this invention, the isocyanurate foammay be prepared by reacting (i) an organic composition having at leasttwo Zerewitinoff active hydrogen atoms i.e. a "polyol", (ii) an organicpolyfunctional isocyanate, (iii) a cell modifying agent such as the DowCorning DC-193 brand trimethyl-end-blocked dimethyl polysiloxane, (iv) ablowing agent such as the Kaiser R-11-B fluorocarbon,trifluoro-chloro-methane; and (v) a di-alkali metal salt of thecomposition of this invention.

Formation of product by practice of the process of this invention may beeffected by using isocyanate and polyol in amount to provide anisocyanate index in the reaction medium of 1-10, preferably 3-6, say 5.Blowing agent is present in amount of 5-20 parts, preferably 10-14parts, say 12 parts. Cell modifying agent is present in amount of 0.1-15parts, preferably 0.3-0.8 parts, say 0.5 parts. Catalyst of thisinvention is present in amount of 0.5-10 parts, preferably 1-4 parts,say 2 parts. (all parts are parts by weight per 100 parts of totalformulation).

The foamed isocyanurate product is found to be desirably characterizedby cream times in excess of about 10 seconds and typically about 15seconds, by increased heat distortion, and by substantially betterdimensional stability at low temperature eg minus 20° F./dry.

DESCRIPTION OF PREFERRED EMBODIMENTS

Practice of the novel process of this invention may be apparent from thefollowing description of preferred embodiments wherein, as elsewhere inthis specification, all parts are parts by weight unless otherwisespecifically noted.

EXAMPLE I

In this example which represents practice of the process of thisinvention, 393 grams (3 moles) of itaconic acid, 600 grams of water, and640.5 grams of the di-terminal diamine of polyoxypropylene (molecularweight about 427, and containing 4.69 milli-equivalents of primary amineper gram) are heated to reflux for 8.5 hours. Supercell filter aid isadded and the reaction mixture is filtered hot and then stripped at 0.5mm Hg in a rotary drum drier with a bath temperature of 95° C.

On cooling, a clear viscous liquid is recovered having an acidity of3.26 milliquivalents per gram and corresponding to the followingformula: ##STR15## R" is a polyoxypropylene residue (of molecular weightof about 400) having terminal carbon atoms to which the nitrogen atomsare bonded.

EXAMPLE II

In this example which represents practice of the process of thisinvention, 526 grams (4.03 moles) of itaconic acid, 600 grams of water,and 470 grams (2 moles) of the diterminal diamine of polyoxypropylene(molecular weight about 235, and containing 8.53 milliequivalents ofprimary amine per gram) are heated to reflux for 8 hours. Supercellfilter aid is added and the reaction mixture is filtered hot and thenstripped at 0.5 mm Hg in a rotary drum drier with a bath temperature of95° C.

On cooling, a light, tacky flowable, viscous resin is recovered havingan acidity of 4.74 milliequivalents per gram, a nitrogen content of6.35% and corresponding to the following formula: ##STR16## R" is apolyoxypropylene residue (of molecular weight of about 200) havingterminal carbon atoms to which the nitrogen atoms are bonded. Thedi-potassium salts is formed by adding 2 moles (per mole of acid) of 85%potassium hydroxide (in 20% aqueous solution) at 50° C. andfiltering.--the di-(tetramethylammonium) salt may be similarly preparedfrom tetramethylammonium hydroxide.

EXAMPLE III

In this example which represents practice of the process of thisinvention, 131 grams (1 mole) of itaconic acid, 100 grams of water, and1030 grams (0.5 mole) of the di-terminal di-amine of polyoxypropylene(molecular weight about 2060, and containing 0.97 milliequivalents ofprimary amine per gram) are heated to reflux of 98° C.-100° C. for 19hours. Water is removed by azeotropic distillation with 500 ml oftoluene, which is added during the course of the reaction. Supercellfilter aid is added and the reaction mixture is filtered hot and thenstripped at 0.5 mm Hg in a rotary drum drier with a bath temperature of138° C.

On cooling, a light brown viscous liquid is recovered having an acidityof 0.82 milliequivalents per gram and corresponding to the followingformula: ##STR17## R" is a polyoxypropylene residue (of molecular weightof about 2030) having terminal carbon atoms to which the nitrogen atomsare bonded.

Results comparable to those of Examples I-III are achieved if the amineis as follows:

    ______________________________________                                        Example     Amine                                                             ______________________________________                                        IV          tri-terminal tri-primary amine                                                of polyoxypropylene of m. wt.                                                 of 400 (as marketed under the                                                 trademark Jeffamine T-403);                                       V           di-terminal di-primary amine                                                  of polyoxyethylene-polyoxypropylene                                           of m. wt. of 600 (as marketed                                                 under the trademark Jeffamine ED-600)                                         etc.                                                              ______________________________________                                    

EXAMPLE VI

In this example which represents practice of the process of thisinvention, 432 grams (3 moles) of alpha-methylene glutaric acid, 600grams of water, and 640.5 grams of the di-terminal diamine ofpolyoxypropylene (molecular weight about 427, and containing 4.69milliequivalents of primary amine per gram) are heated to reflux for 8.5hours. Supercell filter aid is added and the reaction mixture isfiltered hot and then stripped at 0.5 mm Hg in a rotary drum drier witha bath temperature of 95° C.

On cooling, there is recovered product and corresponding to thefollowing formula: ##STR18## R" is a polyoxypropylene residue (ofmolecular weight of about 400) having terminal carbon atoms to which thenitrogen atoms are bonded.

EXAMPLE VII

In this example which represents practice of the process of thisinvention, 474 grams (3 moles) of alpha-methylene adipic acid, 600 gramsof water, and 640.5 grams of the di-terminal diamine of polyoxypropylene(molecular weight about 427, and containing 4.69 milliequivalents ofprimary amine per gram) are heated to reflux for 8.5 hours. Supercellfilter aid is added and the reaction mixture is filtered hot and thenstripped at 0.5 mm Hg in a rotary drum drier with a bath temperature of95° C.

On cooling, there is recovered product acid corresponding to thefollowing formula: ##STR19## R" is a polyoxypropylene residue (ofmolecular weight of about 400) having terminal carbon atoms to which thenitrogen atoms are bonded.

In certain of the Examples which follow, the following properties aremeasured:

Cream time (seconds)--the time interval beginning with mixing of theisocyanate and the B-component (a standard mixture containing thepolyol, catalyst, blowing agent, surfactant, and fire retardant) andending when the composition changes color from dark brown to creamcolor;

Rise time (seconds)--the time interval beginning with mixing of theisocyanate and the B-component and ending when the foam has stoppedrising;

Tack-free time (seconds)--the time interval beginning with mixing of theisocyanate and the B-component and ending when the surface of the foamceases to be tacky when touched;

Density (pounds per cubic foot)--the weight of a given volume of theproduct;

K-factor (BTU.in/h.ft² °F.)--as measured by ASTM test C 177-63 usingDupont modified guarded hot plate;

Elongation at Break (%)--as measured by ASTM test D-638;

Tensile strength (psi)--as measured by ASTM test D-638;

Tensile Modulus (psi)--as measured by ASTM test D-638;

Flexural Strength (psi)--as measured by ASTM test D-790;

Flexural Modulus (psi)--as measured by ASTM test D-790;

Shore D-Hardness 0-10 seconds--as measured by ASTM test D-2240;

HDT (°C., 264 psi/66 psi)--as measured by ASTM test D-648;

Izod Impact Strength (ft lbs/in)--as measured by ASTM test D-256;

Compressive Strength (psi)--as measured by ASTM test D-1625-73;

Heat Distortion (°C.)--as measured by the temperature at which astandard sample is depressed 0.1 inches at a load corresponding to 10%of its Compressive Strength with Rise;

Closed Cells (%)--as measured by ASTM Test D-2856-70;

Dimensional Stability (%)--as measured by ASTM test D-2126-75--modifiedin that the sample actually used had dimension of 2"×2"×2" instead of4"×4"×4";

Flammability--as measured by the Butler Chimney Test--ASTM testD-3019-73. Preferred practice based upon the inherent dangers due topossible flammability of various compositions including urethanes,suggest that the reader be advised that numerical or other data fromthis test are not intended to reflect hazards presented by this or anyother material under actual fire conditions. The data represent thebehavior of the tested material under specific controlled testconditions.

EXAMPLE VIII

In this example which represents practice of the process of thisinvention, the preparation of a cured isocyanurate foam is carried out.

A B-component is first prepared containing the following:

(i) 159 grams of polyol--a polyoxyethylene adduct of a novolak resin ofhydroxyl number 187, and an average functionality of 2.5;

(ii) 3 grams of silicone surfactant--the Dow Corning DC-193 brand oftrimethyl and blocked dimethyl polysiloxane;

(iii) 72 grams of fluorocarbon--the Kaiser R-11-B brand oftrifluoro-chloro-methane;

(iv) 12 grams of a 50% (in polyethylene glycol of molecular weight 300)solution of the dipotassium salt of the acid product of ExampleI--prepared by addition to 155.4 g of the acid product of Example I in50 ml methanol, of an equivalent amount (25.5 g) of potassium hydroxide,in 50 ml methanol (i.e. two moles of potassium hydroxide per mole ofsaid product) and of polyethylene glycol.

To this B-component is added 354 grams of a phosgenatedaniline-formaldehyde condensate of functionality 2.7 and an NCOequivalent weight of 134. The mixture is vigorously stirred and thenpoured into a box mold and allowed to rise.

    ______________________________________                                        Property            Time (seconds)                                            ______________________________________                                        Cream Time           15                                                       Rise Time           140                                                       Tack-free Time      150                                                       ______________________________________                                    

The properties of the product foam are listed in the table which followsExample IX*.

EXAMPLE IX*

In this control example, the procedure of Example VIII was followedexcept that

(i) 160.8 grams of polyol was used;

(ii) 6 grams of a 50% solution (in polyoxyethylene triol having averagemolecular weight of 700) of potassium octoate, a prior art curing agent,was used in place of the 12 grams of the dipotassium salt solution ofExample VIII.

(iv) 358.2 grams of isocyanate was used in place of 354 grams as inExample VIII.

    ______________________________________                                        Property            Time (Seconds)                                            ______________________________________                                        Cream Time          5-6                                                       Rise Time           65                                                        Tack-free Time      100                                                       ______________________________________                                    

This control foam is less satisfactory than is the experimental foam.The cream time and the rise time in particular are much too low to besatisfactory in commercial practice. For proper commercial use, theminimum cream time in a panel-line formulation for example, should beabout 12 seconds and preferably 15-20 seconds as is the case withExample VIII.

    ______________________________________                                        Property    Example VIII  Example IX*                                         ______________________________________                                        Density (pcf)                                                                             2.15          2.20                                                K-factor    0.128         0.115                                               Compressive                                                                   strength                                                                      with rise (psi)                                                                           36.41         36.0                                                across rise (psi)                                                                         13.39         11.39                                               Heat distortion (°C.)                                                              202           170                                                 Closed cells (%)                                                                          90.61         92.72                                               Dimensional                                                                   stability                                                                     ______________________________________                                                     Vol.  Wt.    Linear                                                                              Vol.  Wt.  Linear                             ______________________________________                                        158° F./100%                                                           relative                                                                      humidity (%)                                                                              +9.1   -2.8   +5.6   +6.7 -4.5 +5.0                               180° F./Dry (%)                                                                    +5.9   -1.6   +3.9   +5.3 -2.4 +3.9                               -20° F./Dry (%)                                                                    -4.5   -1.4   -2.8  -11.4 -5.9 -6.8                               Butler Chimney Test:                                                          Weight retained (%)                                                                              85.6               90.7                                    Time to extinguish                                                            (seconds)          14                 10.7                                    Flame height                                                                  (inches)           11+                8.16                                    Friability                                                                    (% weight loss)    8.5                5.4                                     ______________________________________                                    

The clear superiority of the foam of Example VIII over that of ExampleIX* is apparent. In addition to the above comments, particular attentionis directed to the generally superior properties including (i) improvedheat distortion, (ii) volume and linear dimensional stability at lowtemperature, (iii) weight stability, etc.

EXAMPLE X

In this example which represents practice of the process of thisinvention, the preparation of a cured epoxy resin is carried out.

The uncured epoxy resin (100 grams) which is used as charge isidentified as a liquid diglycidylether glycol ester of bisphenol A epoxyresin Eq. Wt. 190.

Curing of the so-prepared epoxy resin (100 g) is effected by additionthereto of

(i) 30 parts of a condensation product of formaldehyde and aniline ofequivalent weight 50, a polyaromatic polyamine curing agent, (marketedunder the trademark JEFFAMINE AP-22).

(ii) 20 parts of a 20 w% solution in benzyl alcohol of the acceleratorcomposition prepared by the process of Example I.

This mixture of components was mixed thoroughly, degassed, poured intoaluminum molds, and cured for seven days at ambient conditions ca 25° C.

The properties of the Formulation were determined on samples cut fromthe castings.

    ______________________________________                                        Properties of cured 1/8" casting                                                                       Value                                                ______________________________________                                        Izod impact strength (ft-lbs/in.)                                                                      0.61                                                 Tensile strength (psi)   9,300                                                Tensile modulus (psi)    404,000                                              Elongation at break (%)  5.1                                                  Flexural strength (psi)  15,000                                               Flexural modulus (psi)   424,000                                              Shore D Hardness (0-10 sec.)                                                                           86-84                                                HDT (°C., 264 psi/66 psi)                                                                       44/48                                                ______________________________________                                    

Flexural samples were cut and immersed in several chemicals for 28 days.All tests were conducted at ambient temperature of ca 25° C. except thatin distilled water which was carried out at 40° C. After removal fromthe chemicals, flexural strength of the immersed samples was determined.Pertinent retention of flexural strength was then computed with thefollowing results:

    ______________________________________                                                             % Retention of                                           Sample immersed in   Flexural Strength                                        ______________________________________                                        Isopropanol          104                                                      Xylene               104                                                      Acetic acid (25%)    89                                                       Sodium Hydroxide (50%)                                                                             115                                                      Sulfuric acid (30%)  102                                                      Distilled water      88                                                       ______________________________________                                    

It will be apparent from inspection of the above properties that thecured epoxy formulations are outstanding with respect to strength andretention of strength after immersion in various chemicals.

EXAMPLE XI*

In this control example, the procedure of Example X is duplicated exceptthat curing is carried out in the absence of the accelerator.

After seven days cure at ambient temperature, the formulations were sobrittle and undercured that it was not possible to cut samples for thetests from the castings. It was apparent that the formulations weretotally unsatisfactory and of low strength.

EXAMPLES XII-XIII*

A liquid accelerating mixture for use in conjunction with aromatic aminecurvatives is prepared by dissolving 20 g. polyoxypropylene-alpha, omegaBis (pyrrolidinone-3-carboxylic acid) in 80 g benzyl alcohol.

The above mixture is combined into an epoxy system as follows

    ______________________________________                                        Formulation:                                                                  ______________________________________                                        Liquid DGEBA epoxy resin (Equivalent weight 190)                                                          100 parts                                         Aromatic polyamine Jeffamine AP-22 brand                                                                  30 parts                                          of the condensation product of formaldehyde                                   and aniline                                                                   Accelerator mixture described above                                                                       20 parts                                          ______________________________________                                    

The formulation is mixed thoroughly degassed and poured into aluminummolds and cured for seven days under ambient conditions. The castingsare then cut into samples and tested with the following results:

    ______________________________________                                        Properties of cured 1/8" casting:                                             ______________________________________                                        IZOD impact strength ft.-lbs./in.                                                                      0.61                                                 Tensile strength, psi    9300                                                 Tensile modulus, psi     404000                                               Elongation at break, %   5.1                                                  Flexural strength, psi   15000                                                Flexural modulus, psi.   424000                                               Shore D hardness, 0-10 sec.                                                                            86.84                                                HDT, °C. 264 psi/66 psi                                                                         44/48                                                ______________________________________                                    

Flexural samples were cut and immersed in several chemicals for 28 days.After removal from the chemicals, flexural strength of the immersionsamples was determined. Percent retention of flexural strength was thencomputed with the following results--

    ______________________________________                                        Sample immersed in                                                                             Percent Retention, Flex. strength                            ______________________________________                                        Isopropanol, R.T.                                                                              104                                                          Xylene, RT.      104                                                          Acetic acid, 25% R.T.                                                                          89                                                           Sodium hydroxide 50%, R.T.                                                                     115                                                          Sulfuric acid, 30%, R.T.                                                                       102                                                          Distilled water, 40° C.                                                                 88                                                           ______________________________________                                         R.T. means Room Temperature                                              

Castings cured without the accelerator mixture (Example XIII*) werebrittle and undercured after 7 days curing at ambient temperatures.Samples could not be cut from such castings. In contrast the castingscured with the accelerator mixture (Example XII) were properly cured,not brittle and readily cuttable.

Although this invention has been illustrated by reference to specificembodiments, it will be apparent to those skilled in the art thatvarious changes and modifications may be made which clearly fall withinthe scope of this invention.

We claim:
 1. The method of curing an uncured epoxy resin whichcomprisescuring 100 parts of said uncured epoxy resin in the presence ofaromatic polyamine curing agent and 1-15 parts of an accelerator##STR20## wherein x is an integer of 0-2; a is an integer of at least 2;R"' is a polyoxyalkylene chain having terminal carbon atoms to which thenitrogen atoms are bonded; and the molecular weight of R"' is 200-2100.2. The method of curing an uncured epoxy resin which comprisescuring 100parts of said uncured epoxy resin in the presence of 20-40 parts ofaromatic polyamine curing agent and 1-15 parts of an accelerator##STR21## wherein x is an integer of 0-2, and R" is a polyoxyalkylenechain of molecular weight of about 200-2100 having terminal carbon atomsto which the nitrogen atoms are bonded.
 3. The method of curing anuncured epoxy resin as claimed in claim 2 wherein x is zero.
 4. Themethod of curing an uncured epoxy resin as claimed in claim 2 wherein R"is polyoxyethylene.
 5. The method of curing an uncured epoxy resin asclaimed in claim 2 wherein said accelerator is the reaction product oftwo moles of itaconic acid and about one mole of polyoxyethylenediamine.